Cyanogenic Poison Protects From Herbivores

close up of a yellow flowering acacia tree with a blurry background

Biological Strategy

Wattle

AskNature Team

Image: Lies Van Rompaey / Flickr / Some rights reserved

Protect From Animals

Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

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Send Chemical Signals (Odor, Taste, Etc.)

Tastes, odors, and hormones are all chemical signals that can float through the air or water, or be applied to solid surfaces. Chemicals are important for signaling and communication; even humans, with our underdeveloped sense of smell, are influenced by chemicals more than we realize. Chemical signals are often specific to the living system intended to receive them, and are often relatively weak, dispersing upon moving through liquids or gases. To ensure that chemical signals reach their target, living systems create unique chemical signals and methods of dispersal. One example is an orchid that is pollinated by dung beetles, and therefore distributes a dung-smelling aroma to attract them.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The leaves of acacia trees protect from being eaten by producing a cyanogenic poison.

Image: Emily Harrington /

Acacia responding to browsing by giraffe: a. Leaves prior to damage; b. When damaged by browsing, the leaves fill with a cyanogenic poison; c. At the same time, the leaves release ethylene gas through their pores which gets carried downwind to alert other trees. Artist: Emily Harrington. All rights reserved.

Image: Avishai Teicher / Wikimedia commons /

Acacia cyanophylla

“The African acacias, well-protected though they may be by their thorns, use distasteful chemicals in their leaves as a second line of defence. Furthermore, and most remarkably, they warn one another that they are doing so. At the same time as they fill their leaves with poison, they release ethylene gas which drifts out of the pores of their leaves. Other acacias within fifty yards are able to detect this and as soon as they do so, they themselves begin to manufacture poison and distribute it to their leaves.” (Attenborough 1995:70)